Tag-Along Aux Fuel Tank fuel pump or not

[JSaul]

For those that have been using the Tag-Along Aux Fuel Tank that joe2lmaker created; are using letting gravity do the work or have you added a fuel pump?

I have used a fuel pump for the last 2 years on mine and it has worked but had some issues of late that have me of going to gravity feed to simply the setup.

I removed the fuel pump and rerouted the fuel lines and going to try the gravity feed. How long does it take to fill the tank. With the fuel pump, I would flip the power on and open the valve once the single bar started flashing.

I am going to get a try next weekend trying gravity feed but concerned about timing and backflow, etc..

Looking for input fro other users of this tank.

Thanks,

Jim

 

[NTXFJR]

Just a thought, you could try emptying your main tank, and with the bike up on the center stand, open the aux valve and set a timer. I ran a static test like this last week with my newly installed generic aux tank in the driveway, then took it out on the interstate to run the same test and experienced the same results. For my system with 5/16" fuel line, it drained 3.5 gallons in around 20 minutes, or around 10.5 gallons per hour. For reference, at an interstate speed of 85 mph getting 36 mpg, my bike's fuel consumption rate works out to around 8/10 gallon in 20 minutes, or around 2.3 gallons per hour.

Iirc, Joe's tagalong tank packs around 4.7 gallons, so at the interstate speed referenced above, that 4.7 gallons could drain in 2 hours or less and still keep up with the consumption rate. 4.7 gallons works out to be around 70% of the main tank's capacity, so waiting until the fuel gauge is 2 segments or less to open the valve should be fine.

 

[JSaul]

I did the static test this afternoon and the results were poor. It went from a flashing bar to a single bar in 25 minutes and after an hour I am at 2 bars. I checked the lines yesterday and have no kinks or bad bends to contend with.

I may have to install the fuel pump back for my piece of mind. more to come...

 

[NTXFJR]

Might double check the vent line. What size fuel line do you have?

 

[RossKean]

Are you using 5/16" lines? What is the inside diameter of your fittings and petcock? Just takes one restriction...

 

[JSaul]

5/16 fuel line. vent line is the same. I changed the gas cap to one of the keyless CNC caps and I believe that may be some of the slowness. I changed all the lines today and was too slow for me. I added a new fuel pump back into the scenario and it empties the TAT in 12 minutes. This is closer to what it was before. It was filling in 8 minutes before. I suspect the gas cap. I have it to where I can predict it. Will do a road test net weekend with a quick trip to key west and back. I will try the stock gas cap at some point to see if that is the difference in 4 minutes... Either way, I have a very predictable time 12 minutes.

 

[RossKean]

Petcock internal diameter also 5/16"?

 

[NTXFJR]

Good point. the internal port sizes of any of the fuel line components can have a big impact. The fuel pump might be masking some of it. I looked at port sizing closely when selecting valves and such. The fuel cap even if not vented shouldn't make a difference in flow rate, if it does, you might want to make sure that the vent line and it's tank connection are not restricted.

 

[JSaul]

I am using the petcock supplied with the tank. I have been running this setup for about 3 years and only recently started having issues. When I first put the tank on with fuel pump it would fill in 8 minutes.

What changed: Replaced OEM gas cap with aftermarket CNC keyless cap

Replaced faded tank bag with exact same

This year I was having the issue with no fill to slow fill. Thought I had a bad petcock and replaced petcock with same model and size as the original. This year I was having the issue with no fill to slow fill.

I have now replaced entire fuel line(5/16"), replaced the fuel pump and quick connectors.

I can live with the 12 minutes but the next test I will unscrew the gas cap and time the fill rate as I suspect the new fuel cap is limiting the venting that the OEM allowed.

The only thing other than the gas cap to replace would be bulkhead fitting.

More to come........

 

[Mr_Canoehead]

The amount of hydraulic head will make a big difference to the gravity feed rate. It will slow dramatically as you get to the bottom of the tank. The difference in height between the bottom of the TAT and the stock tank is only a couple of inches.

I would also check the vent on the TAT. If it's blocked, your transfer rate would go way down.

Which pump are you using?

 

[JSaul]

I was using a K&N that is rated for 32 gallons per hour between 4-7 psi. This was part of the original setup that transferred all fuel in 8 minutes. By the math that is almost spot on.

I just replaced it with a Holley fuel that is almost identical in everything but the label. It transferred in 12 minutes. The only thing different in the setup now is the gas cap.

I am going to retest the transfer this weekend with OEM gas cap.

 

[JSaul]

OEM gas cap reduced fill rate by 2 minutes. So was able to empty transfer tank in 10 minutes. I am going to live with this for now.

 

[Shane]

I've been using gravity only with my TAT since installed several years ago.

5/16 line, with Parker coupler inline, and a CNC keyless aftermarket vented fill cap.

As stated above, the initial transfer rate with full aux and near-empty main is quick at first, then slows as the main tank begins to even up the levels in the two vessels.

At speed, and from a 1-2 bar on the main tank starting point, the main tank will go back to at least 3/4 full within 20 minutes, at which point I just leave the valve open until it's time to stop, except when climbing mountain passes and the TAT is nearly empty (to prevent reversal).

I don't know how fast the TAT would drain into anything else, like a bucket on the floor. That's ok though, because I'm not trying to fill the main tank with anything but atmospheric pressure via gravity.

All the best,

Shane

 

[PhilJet09]

I was using a K&N that is rated for 32 gallons per hour between 4-7 psi. This was part of the original setup that transferred all fuel in 8 minutes.
I am going to retest the transfer this weekend with OEM gas cap.

I'm running this same set up. K&N pump, 5/16 lines, OEM cap and mine drains in just under 10 minutes. I put a programmable timer the size of a postage stamp in my circuit and set it for 10 minutes, because I CRS.

 

[Joe2Lmaker]

These will work relying on gravity alone.

The first two prototypes, mine and dcarver's being exceptions. Those two had copper drain lines. The diameters were probably too restrictive.

The production tanks were plumbed differently, however shared the same valve.

In 2011, a rider using one of those tanks with a gravity feed set-up placed 14th in the Iron Butt Rally. For me, this was sufficient evidence for gravity only.

In 2013, another rider using one the production tanks with a gravity feed set-up placed 6th in the IBR.

I wish I had a complete list. I'm proud of these things. I wonder where they've been.

 

[PhilJet09]

Oh I'm sure mine would gravity feed just fine, but I'm more of a make-it-happen than a let-it-happen person. I find it entertaining to open a valve, flip a switch and watch the fuel gauge go back up. Simple things.

 

[Poolboytoo]

I have a tag along tank with 5/16 line and a Faucet fuel pump and even with the fuel pump installed it will still gravity feed. I always let it get down to 2-3 bars and transfers fuel. 13 minutes I just let it go for 15 minutes to make sure it all has been transferred. need to install something to remind me i turned ON the pump.lol

 

[dcarver]

I use a delay relay set for 20 minutes run time. I've run gravity and pump, like the pump better. Instant gratification..

 

[Poolboytoo]

Oh yea, I think Philjet was telling me about those in Colorado. Just looked on line found a bunch, looks easy enough. Thanks